Switch circuit and actuating mechanism



April 11, 1961 E. J. MARTIN ETAL SWITCH CIRCUIT AND ACTUT ING MECHANISMFiled NOV. 29, 1957 ATTORNEY contacts close.

United States Patent O SWITCH CIRCUIT AND ACTUATING MECHANISMl Edward J.Martin, Pleasant Ridge, and John M. Farrell, Detroit, Mich., assignorsto General Motors Corporation, Detroit, Mich., a corporation of DelawareFiled Nov. 29, 1957, Ser. No. 699,695

Claims. (Cl. S18-134) This invention relates to electric clocks and moreparticularly to an improved switch mechanism and circuit for such clocksand similar applications.

Electric clocks adapted for energization from direct y voltage sourceshave been devised which utilize an elecment of tilms and oxides on thecontact surfaces which` prevents good electrical contact withoutsufficiently high contact pressure to penetrate such films and oxides.ln accordance with this invention, means are provided for momentarilyincreasing the contact pressure when the This is accomplished by the useof an electromagnet or pull-in coil adjacent the movable contact andwhich is energized for a short duration by the discharge of a condenser.

Additionally, in such clocks it is desired to operate the switchcontacts synchronously with the balance wheel without a directmechanical connection so that the con-v tacts may be contained within asealed casing to promote long -operating life. This is accomplished inaccordance with this invention by a magnetic coupling between a drivingmember on the balance wheel and a switch actuator. This arrangement alsopermits the switch to be constructed as a unitary component so that itmay be readily replaced.

A more complete understanding of this invention may be had from thedetailed description which follows takenl with the accompanying drawingsin which:

Figure 1 is a fragmentary view showing the general arrangement of aclock embodying the present invention;

Figure 2 is a view taken on lines 2-2 of Figure 1;

Figure 3 is a diagrammatic representation of the inventive switchmechanism and circuit;

Figure 4 is a diagrammatic representation of an alternative embodimentof the switch operating mechanism; and

Figure 5 is an enlarged pictorial view with portions cut away to showdetails of the switch structure.

Referring now to the drawings there is shown an illustrative embodimentof the invention in an electric clock of the electromagnetic impulsetype. In general, the clock comprises a balance wheel assembly with anassociated electromagnetic drive 12 provided with an energizing circuit14. The circuit includes a switch 16 operatively coupled with thebalance wheel assembly 10 for synchronous operation therewith and anelectromagnet 18 is associated with the switch 16 to ensure uniformlygood electrical contact operation.

Referring now to Figures l, 2, and 3, the invention will be described indetail. The balance wheel assembly ice 10 comprises a balance wheel 20mounted upon a pivot staff 22 which is resiliently constrained by thehairspring 26. Periodic oscillation of the balance Wheel is maintainedby the magnetic lield of the pole pieces 24 of the electromagnetic drive12. An indicator drive train including mechanism 60 is driven by anarmature (not shown) coupled with pole piece extensions 25. A periodicmagnetic impulse is provided for the pole pieces 24 and 25 by theenergizing circuit 14. This circuit includes a voltage source 28 havingone terminal connected to a point of reference potential or ground andthe other terminal connected through the energizing or driving coil 30of electromagnetic drive 12 and thence through the Y and 36, a resistor46 and condenser 48 are serially connected across the contacts.

The electromagnet 18 has a pole piece 3S disposed adjacent the contactsupport member 4t) which is of magnetic material and subject toattraction by the magnetic field of the electromagnet. The supportmember 40 is secured to the switch actuatingV arm 42 for displacementtherewith an'd the arm is mounted at one end upon the support pin 50 forangular deflection by pivotal or ilexingV motion o f the arm 42 aboutthis support. The free end of the arm '42 supports a permanent magnet 52which is coupled by magnetic linkage with a driving member or armature54. The armature 54 is mounted upon the pivot staff 22 as part of thebalance wheel assembly and thus has an oscillatory motion concurrentwith therbalance wheel. The armature S4 has rim elements 56 and 58 ofmagnetic material which are axially oiiset from each other.V VTheelement 58 has a circumferential length somewhat less than theoscillatory displacement of the balance wheel 20. The magnet 52 servesto couple the switch actuating arm 42 to the elements 56 and 58 of thearmature by magnetic linkage therewith. Since the arm 42 is constrainedagainst motion in the plane of the armature but has freedom of movementin a transverse plane, rotation of the armature will cause the arm 42 toreciprocate in following the rim elements 56 and S8. This causes openingand closing of the contacts 34 and 36 depending upon the direction ofmovement of the armature 54.

In Figure 4, there is shown a modification of the actuating mechanismfor the switch 16. In this modification the armature 64 has a rimincluding circular element 66 and a radial projection orelement 68 ofcircumferential extent somewhat less than the oscillatory displacementof the balance wheel 20. The switch 16 is oriented relative to thearmature 64 so that the actuating arm 42 has freedom of movement in aplane transversely of the armature 64 or parallel to the axis thereof.Accordingly,V

- manent magnet 52. Accordingly, the switch contacts 34 and 36 will beopened or closed depending upon the direction of movement of thearmature 64.

As shown in Figure 5, the switch 16 is suitably constructed as a unitarycomponent to facilitate replacement in the maintenance of the clock. Theswitch 16 thus is provided with a casing 62 which may be hermeticallysealed and lilled with a liquid or gas to promote long service life ofthe switch. ln this construction, the entire casing 62 or at least theend wall 70 is of non-magnetici material to permit flux linkage of thepermanent magnet 52 with the external armature. The electromagnet 18 maybe coupled with the contact support member 40 by a magnetic plug 72 inthe wall of the casing 62,

The invention will be further understood from a consideration of a cycleof operation. Consider first the balance wheel in oscillation at itsclockwise limit of rotative displacement. In this position, the armature54 has its rim element 56 opposite the magnet 52 and, accordingly, theactuating arm 42 opens the contacts 36 and 34. The voltage source 2Scauses a current liow, limited by the resistance value of driving coil30, to charge the condenser 44. As the balance wheel 22 swings back in acounterclockwise direction toward its reference position,V

the magnet 52 and actuator arm 42 follow the rim element 58 and thus thecontacts 34 and 36 are closed. Accordingly, the condenser 44 immediatelydischarges through the low resistance path of the winding 32 ofelectromagnet 118 and the closed contacts 34 and 36 to ground. Thisdischarge current causes the electromagnet 18 to develop an attractiveforce on the support member 40` which pulls the movable contact 36 intoengagement with ixed contact 34. A momentary increase of contactpressure is produced to penetrate any oxides or other film on thecontact surfaces. The discharge of condenser 44 lowers the potentialthereacross and permits a current impulse to be delivered from voltagesource 28 through the driving coil 30. This current impulse in thedriving coil 30 produces a magnetic impulse in the pole pieces 24 toimpart rotative effort to the balance wheel 22 to sustain oscillationsthereof. The time constant of the discharge path provided for condenser44 is sufficiently low that the pull exerted by the electromagnet 18diminishes to a negligible value prior to the rotation of the balancewheel 22 to its counterclockwse limiting position. Thus, when the rimelement 56 of armature 54 is opposite the magnet 52 in itscounterclockwise swing, the same force is required for opening as isrequired for closing since the influence of the electromagnet in thisposition is negligible. With the contacts open the condenser 44 isrecharged and during the clockwise rotation of the balance wheel 20, thecontacts 34 and 36 are again closed by coaction of the armature 54 andpermanent magnet 52. Simultaneously, a driving impulse is developed bythe driving coil 30 and a current impulse is delivered through the coil32 of the electromagnet 18 in the same manner as previously described.Accordingly, the balance wheel continues its clockwise rotation to itslimiting position during which the contacts are again opened and thecondenser 44 is recharged. This cyclic operation is, of course, repeatedat a rate corresponding to the period of the balance wheel assembly 10.

Although the description of this invention hasv been given with respectto a particular embodiment, it is not to be construed in a limitingsense. Numerous modifications and variations within the spirit and scopeof the invention will now occur to those skilled in the art. For adefinition of the invention, reference is made to the appended claims.

We claim:

l. An energizing circuit for a clock comprising a voltage source, anoscillatory member having an electromagnetic drive including anenergizing coil, a switch having a fixed contact and a movable contact,a reciprocable actuator connected with the movable Contact, a drivingmember connected with the oscillatory member and being movabletransversely of the actuator and magnetically coupled therewith foralternate opening and closing of the contacts in synchronism with theoscillations of the oscillatory member, an electromagnet mountedadjacent said movable contact; said energizing coil, electromagnet, andswitch contacts being serially connected across the voltage sourcewhereby closing of said contacts causes a current impulse to energizesaid energizing coil to maintain oscillation of the balance wheel, and acondenser connected across said electromagnet and said switch contactswhereby closing of said contacts causes a current impulse from thecondenser through the electromagnet to increase the engaging pressure ofthe contacts.

2. An energizing circuit for a clock comprising a voltage source, anoscillatory balance wheel having an electromagnetic drive including adriving coil, a switch hav ing a xed contact and a movable contactoperatively connected with the balance wheel for alternate opening andclosing of the contacts in synchronism with the oscil latons of thebalance wheel, a condenser, said voltage source and said driving coilserially connected across the condenser and providing a relatively longtime constant charging circuit for the condenser, an' elcctromagnetmounted adjacent said movable contact and having an energizing coilconnected serially with said switch contacts acrossV said condenser andproviding a relatively short time constant discharging circuit for thecondenser whereby closing of said contacts causes a current impulse toenergize said driving coil to maintain oscillation of the balance wheel,and causes a current impulse from the condenser through theelectromagnet coil to cause momentarily increased engaging pressure ofthe contacts.

3. A switch having a pair of oppositely disposed contacts, one of thecontacts being movable in the direction toward and away from the other,an actuator adapted for reciprocating motion and being operativelyconnected for displacement of the one contact in said direction, arotatable driving member adjacent the actuator and having a continuousmagnetic rim portion including a pair of circumferentially displacedmagnetic elements offset from each other in the direction of saidreciprocating motion, a permanent magnet mounted on said actuatoradjacent said elements for magnetic linkage therewith through asubstantially constant air gap whereby rotation of the driving membercauses the actuator to execute reciprocating motion and operates theswitch contacts due to the attraction between the magnet and the rimportion.

4. In combination, a switch having a pair of oppositely disposedcontacts, one of said contacts being movable in the direction toward andaway from the other, an actuator operatively connected for displacementof the one contact and being adapted for movement in said direction, amagnet mounted on the actuator, a driving member movable in a transversedirection, said driving member including a pair of magnetic elementsspaced in said direction and spaced in the transverse direction, saidmagnet being effective to couple said actuator with said elementswhereby movement of the driving member in the transverse directioncauses movement of the actuator and the one contact in said direction, avoltage source, an electromagnet mounted adjacent the movable contactand having an energizing coil connected serially with said switchcontacts across said voltage source whereby closing of said contacts bymovement of the actuator energizes the electromagnet to aid the magnetin closing said contacts.

5. In combination, a voltage source, an oscillatory member having anelectromagnetic drive including a driving coil, a sealed casingincluding a non-magnetic wall portion and enclosing a switch, saidswitch including a pair of oppositely disposed contacts, one of saidcontacts being movable in a direction toward and away from the other, anactuator adapted for reciprocating motion within the casing and beingoperatively connected for displacement of the one contact and beingadapted for movement in said direction, a magnet mounted on the actuatoradjacent said wall portion, a rotatable driving member outside thecasing and adjacent said wall portion and having a continuous magneticrim portion including a pair of circumferentially displaced magneticelements offset from each other in the direction of said reciprocatingmotion, said magnet coupling said actuator with said l driving memberwhereby rotation of the driving member Refefnls Cited in th 1 0f thiswiet 'causes actuation of the one switch contact, and a voltage UNITEDSTATES PATENTS source serially connected with said driving coil and said1,970.412 I Bates Aug 14, 1934 switch contacts for periodic energizationof said electro- 5 2,256,037 n Henningl et a1, Dec, 16, 1941 magneticdrive to sustain oscillations of said oscillatory 2,320,208 Wurth May25, 1943 member. 2,575,650 Alexander Nov. 20, 1951

